1. Field of the Invention
The invention is related to cyclic oligomeric compounds.
2. Description of Related Art
There are two approaches in nanopore sequencing. In the first approach, the proteinaceous pore, alpha-Hemolysin, is used to reconstitute a planar phospholipid bilayer membrane. A black lipid membrane (BLM) is formed on a thin Teflon partition with a hole in the middle several tens of microns in diameter. The partition separates identical aqueous media (e.g. 1 M KCl with buffer at neutral pH) in a trough. A voltage is applied so as to drive an ionic current through the open pore. If single stranded DNA is introduced into the cis chamber (the chamber with the negative electrode) current blockades are observed during polyanionic DNA translocation through the protein pore into the opposite trans chamber. (Henrickson et al., “Driven DNA Transport into an Asymmetric Nanometer-Scale Pore,” Phys. Rev. Lett., 85, 3057 (2000). All referenced publications and patent documents are incorporated herein by reference.) The limitations with this approach are that 1) proteins are fragile, 2) scaling up for industrial production is not feasible 3) the nanopore is highly asymmetric in size and interactions 4) conformational fluctuations within the pore raise the noise level.
To eliminate the problems associated with fragile pores, solid state membranes (such as silicon nitride) were ion beam milled to form a pore for nanopore sequencing (Li et al., “DNA Molecules and Configurations in a Solid-State Nanopore Microscope,” Nature Mat., 2, 611 (2003)). The disadvantages with this approach are 1) it is difficult to routinely process holes less than 40 nm in diameter 2) reproducibility of the pore features is difficult 3) the membrane thickness is much larger than the size of a DNA nucleotide 4) interaction between the translocating DNA and the pore cannot be tuned for controlling the translocation (other than through physical variables such as voltage and concentration of solution).